There has a been a long felt need for a monitoring method and system for evaluating the health of a physical system during its operation. Such systems include combustion engines and their associated cooling systems, electrical motors, transmissions, differentials, gear boxes, pumps, compressors, electronic equipment, superconductors, to name a few. It is heretofore been difficult to evaluate the health of such physical systems during operation and to warn the user of a degraded state of health which might lead to impending breakdown and failure of the physical system.
The value of a method which provides an indication of physical system health as a forecast to failure can be unquestioned. Not only can the direct benefits of preventive maintenance be realized, but also the costly and sometimes disastrous consequential damages from failure of a physical system be avoided. For example, with respect to engine driven vehicles, the direct costs from failure of the combustion engine include those incurred in the rebuilding or the repair of the engine while the indirect costs include loss of vehicle availability and readiness, decreased operational efficiencies, shortened vehicle service life, increased costs of maintenance materials, loss of man power and delays. Delays in vehicle availability can, in turn, result in a loss of perishable goods where the vehicle is being used for delivery and can result in construction delays where construction vehicles are involved.
It has been found in those physical systems which produce and exhaust heat (through cooling systems or by direct radiation), that a precursor to failure of such physical systems is either an increase in the waste heat generated by the physical system or a decrease in ability to reject heat into the environment. It should therefore be appreciated that, for the physical systems subject of the present invention, at least some waste heat is produced during operation. The ability of these systems to exhaust waste heat to the ambient environment depends on the temperature of the ambient environment.
Variables other than ambient temperatures may also affect the production of waste heat of the physical system that is to be rejected into the environment. These variables are usually dependent upon the physical system involved. One such variable, for example, is the load placed upon the physical system; this load, in turn, may be expressed as other variables. This load contributes significantly to the waste heat produced thereby. Engines, electrical motors, gear boxes, transmissions, and the like produce waste heat directly in response to load based upon their relative energy efficiencies.
Some physical systems, however, are fairly independent of load. For example, the cooling system of an engine, as a separate physical system from the engine itself, may exhibit a normal capacity for cooling even a degraded engine so that the degraded engine does not fail. However, should the cooling system be degraded, it may allow overheating and failure of the engine even though the engine was previously in good health.
Existing techniques of monitoring physical systems measure, display and generate alarms of one measurement, such as heat. For example, most motor vehicles are equipped with either a temperature gauge or a temperature warning light that responds to coolant temperature to display that temperature or, in the case of a warning light, a warning of an excessive temperature condition is indicated. Such systems do not take into account the ambient temperature of the vehicle's environment. These techniques have not proved suitable for accurately determining the health of the physical system since there is a plurality of variables associated with these systems.
Further, with respect to coolant systems, other warning systems to signal high coolant temperatures have been developed, and some coolant monitors also indicate corrosion and electrically conductive contaminants in the coolant. U.S. Pat. No. 3,475,750 discloses a temperature monitoring system which uses several analog temperature sensors in order to provide a display of operating conditions of an engine. Similar heat sensors are known to disconnect a power supply to an electrical motor should the motor overheat or draw excess current. Likewise, many devices are protected by fuses or circuit breakers which respond to disconnect the device from its power supply when the device is overheated or drawing excessive electrical current.
None of the systems or devices used in the prior art, however, are known to provide a method or apparatus to measure the degradation of a system or to provide a forecast for potential failure of the physical system or to predict an ambient failure temperature for a degraded system. Accordingly, there remains a need for such a method and apparatus.